func (q *commandQueue) Flush(context *opengl.Context) error {
q.m.Lock()
defer q.m.Unlock()
// glViewport must be called at least at every frame on iOS.
context.ResetViewportSize()
for _, g := range q.commandGroups() {
n := 0
for _, c := range g {
switch c := c.(type) {
case *drawImageCommand:
n += len(c.vertices)
}
}
vertices := make([]float32, 0, n)
for _, c := range g {
switch c := c.(type) {
case *drawImageCommand:
vertices = append(vertices, c.vertices...)
}
}
if 0 < len(vertices) {
context.BufferSubData(opengl.ArrayBuffer, vertices)
}
// NOTE: WebGL doesn't seem to have Check gl.MAX_ELEMENTS_VERTICES or gl.MAX_ELEMENTS_INDICES so far.
// Let's use them to compare to len(quads) in the future.
if maxQuads < len(vertices)*opengl.Float.SizeInBytes()/QuadVertexSizeInBytes() {
return fmt.Errorf("len(quads) must be equal to or less than %d", maxQuads)
}
numc := len(g)
indexOffsetInBytes := 0
for _, c := range g {
if err := c.Exec(context, indexOffsetInBytes); err != nil {
return err
}
if c, ok := c.(*drawImageCommand); ok {
n := len(c.vertices) * opengl.Float.SizeInBytes() / QuadVertexSizeInBytes()
indexOffsetInBytes += 6 * n * 2
}
}
if 0 < numc {
// Call glFlush to prevent black flicking (especially on Android (#226) and iOS).
context.Flush()
}
}
q.commands = []command{}
return nil
}